# Thread: Center of Mass and Momentum

1. ## Center of Mass and Momentum

An unstable nucleus with mass of 13.1 x 10^-27 kg initially at rest disintegrates into 3 particles. One of the particles, of mass 4.4 x 10^-27 moves along the positive y-axis with a speed of 5.5 x 10^6 m/s. Another particle, of mass 6.3 x 10^-27 kg moves along the positive x-axis with a speed of 3.6 x 10^6 m/s.
a) find the speed of the third particle
b) at what angle does the third particle move?

2. Originally Posted by Linnus
An unstable nucleus with mass of 13.1 x 10^-27 kg initially at rest disintegrates into 3 particles. One of the particles, of mass 4.4 x 10^-27 moves along the positive y-axis with a speed of 5.5 x 10^6 m/s. Another particle, of mass 6.3 x 10^-27 kg moves along the positive x-axis with a speed of 3.6 x 10^6 m/s.
a) find the speed of the third particle
b) at what angle does the third particle move?
I don't have time to help you much, but consider that there are no net external forces on the particles when the nucleus disintegrates. So the net momentum of the system (which is 0 kgm/s) is conserved.

Now, momentum is a vector, so the momentum components in the x and y directions are also conserved. So set the initial momentum component in the x direction (0) equal to the sum of the final momentum components of the pieces. Do the same for the y direction.

-Dan